Automatic telephone system



Sept. 11, 1956 H. P. BOSWAU 2,762,864

AUTOMATIC TELEPHONE SYSTEM sept. 11, 1956 H. P. BOSWAU 2,762,864

AUTOMATIC TELEPHONE SYSTEM INVENTOR. J/@v Po/m.

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I I I I I I /2I I I@ I I I I I f5 I H kg Pap?j Qzw United States Patent O AUTOMATIC TELEPHONE SYSTEM Hans P. Boswau, Dundee, Ill., assignor to Le'ch Electric Company, a corporation of Illinois Original application December '14, 1948, Serial No.

65,268. Divided and this application June 7, 1950, Serial No. 166,624

21 Claims. (Cl. 179-18) This application is a division of co-pending application Ser. No. 65,218, filed December 14, 1948, now Patent No. 2,573,889, dated November 6, 1951. The invention disclosed herein is concerned with an automatic telephone system and with circuits for use in such system.

The new system employs a switching apparatus as disclosed in the above noted, patent, which may be referred to, for the sake of convenience, as a type of coordinate or crossbar apparatus, or as a type of relay switching apparatus. There are provided a desired number of switches disposed side by side, each having access to a link circuit through the medium of a switch bus having conductors which are multipled to a plurality of sets of units contacts. Each set of units contacts is operable by a units actuator and is associated with corresponding sets of contact ngers disposed in superposed rows for selective engagement by means of tens actuators with sets of removable bare conductor bars. The latter extend serially through all the switches and form the line multiple therefor. The extension of a particular set of conductor bars to a link circuit is accomplished by the selective actuation of a particular tens actuator and a particular units actuator under control of allotter means which is incorporated in each switch and under control of new tens and units guard means which is associated with the switching apparatus.

Some oi the specific objects and features of the invention may be briey summarized as follows:

l. One object is to provide a system having aswitch of the character described comprising tens and units actuators, relay means for operating each actuator, and holding contact means operated by each relay means.

2. Another object is to provide a system having a switch as described, comprising removably mounted conductors forming a line bank multiple representing subscribers lines each associated with a set of conductors in said line bank multiple, conductors forming a switch bus, tens and units actuators for selectively connecting any of said sets of removable conductors with the conductors of said switch bus, individual magnet means for operating each of said tens and units actuators, removably mounted conductors forming an allotter bank multiple, a separate actuator for said allotter bank multiple, and contact means operated by said separate actuator for connecting said individual magnet meanswith predetermined conductors ot' said allotter bank multiple.

3. Another object of the invention is to provide a system having a switch of the class described, which comprises removable sets of conductors forming a line bank multiple, conductors forming a switch bus, tens and units actuators for connecting any set of conductors in said line bank multiple with corresponding conductors of said switch bus, individual magnet means for said tens and units actuators, conductors forming an allotter bank multiple, an allotter actuator, and contact means controlled by said allotter actuator for simultaneously connecting a predetermined tens and a predetermined units magnet to predetermined conductors of said allotter bank multiple.

4. A further object is to provide a system having a switch of the character described, which may be interchangeably operated as a finder or as a connector.

5. Another object is to provide a system having a switching mechanism comprising a plurality of like switches disposed side by side, said switches being arranged in pairs, each pair comprising a iinder and a connector.

. 6. The invention also contemplates as an object to provide a new line lockout circuit comprising a line relay and a cutol relay associated with a line, circuit means for energizing said relays in series relationship incident to establishing a connection, and means for establishing an auxiliary circuit for holding said cutolt relay momentarily operated upon release of said circuit means and consequent release of said line relay.

7. A further object is to provide a new line circuit as defined in the foregoing paragraph, particularly for use with a party line, wherein said cutol relay is equipped with two balanced windings, and circuit means operative on reverting calls, upon release of said line relay, for connecting said balanced windings to the line loop for the purpose of feeding transmitter battery thereto.

8. Still another object is to provide a tens and units guard control circuit for a group of lines having the same tens digit in their numbers, said control circuit comprising a line and a cutoi relay for each line in the group, a tens guard and a units guard relay, and contact means governed by said line and said cutoiT relay for controlling the operation of said guard relays.

9. Another object is to provide subscribers lines in tens and units groups, ten tens allotter bars for each tens and ten allotter bars for each units group, a tens and units guard circuit, and means in said guard circuit responsive to the initiation of a call by a subscriber for selecting the tens and the units allotter bars of the corresponding groups and for marking such bars.

10. The invention also proposes to provide a plurality of iinder switches, each associated with a link circuit, allotter means included in each finder switch and cornprising an allotter magnet, a control circuit including a conductor serially connected to all the link circuit, means for marking said conductor in response to a call initiated by a subscriber, means in an idle link responsive to such marking for causing operation of the allotter magnet associated with the finder of such link, and means operated by said allotter to cause said finder to seize the terminals of said calling line.

11. Another object is to provide allotter means adapted to control the operation of nder switches to seize calling lines, means for seizing said allotter means responsive to the initiation of a call by a line, and relay means for t`reeing said allotter means if seized by a line having trouble in its line circuit.

12. Still another object is to provide a marker circuit which is comon to all links, permitting the use of finder and connector switches of identical construction.

13. The marker circuit, in accordance with another object, contains the digit wiring, thus simplifying changes which may be desired with the regard to digit designations.

14. In accordance with a further object, the marker determines simultaneous actuation of the tens and units magnets in the connector switch, thereby selecting a trunk in response to a single digit dialled by a calling party.

l5. The invention also provides a novel interrupter circuit which comprises a set of relays for controlling the signalling to a calling line, to a pay station or to a trunk, and for driving another set for relays which con trol the ringing on called lines.

.16. The invention further provides, in accordance with still another object, an automatic telephone system furnishing facilities for local calls and fortrunk callsto a manual switching point and including a trunk line and a control circuit therefor, giving access to said trunk line, a link circuit .for .effecting local 4an-d 'trunk calls, respectively, time control disconnect means for causing disconnection of'a local call, and means'in the trunk control circuit for disabling said disconnect means on trunk calls.

17. In connection with trunk line operation, the invention also provides a control circuit which momentarily reverses battery on'trunk calls to start a spurt of tone on pay station lines.

18. As a novel feature, the invention Vfurther provides a set of lockout relays actuated by timing impulses delivered at three-minute intervals to an input conductor by a timer, and means operating in conjunction with a capacitor which is effective upon power failure for dellivering timing impulses to said input conductor at shortened intervals.

19. As another feature, the invention also lprovides relay means for the transmission to the links of time disconnect pulses under control of 'the'relays and the timer which govern the transmission of lockout timing impuless.

20. Other features of the invention'reside in the use of several relays in the link circuit, each for performing several distinct functions.

2l. A novel counting relay circuit is provided using six relays in binary operation in pairs of two for counting ten pulses, thus obtaining ten distinct relay combinations, one for each of ten dial pulses.

22. The use of counting relays for counting dial pulses to furnish information to the marker and-the use of some of these .counting relays in party line ringing is a further feature of the invention, making it possible to use either bridged metallic or divided grounded ringing on any line.

23. As another feature, there are provided iveringing leads for ten rings in conjunction with two separate ringing start links forcode ringing up to ten codes.

The foregoing summary gives Vonly examples .of the objects and features of the invention.

The objects noted in the foregoing statements and other objects and features will be described with reference to the accompanying drawings, in which Fig. 1 is a diagrammatic representation of the new switch structure:

Fig. 2 shows the new switch in diagrammatic side view, as seen when looking in the direction of the arrow along line 2 in Fig. 6;

Fig. 3 iilustrates the new switch from the opposite side, as seen whenlooking in the direction of .the arrow along line 3 in Fig. 6;

Figs. 4 and 5 are diagrammatic front and rear views of the switch;

Fig. 6 is a diagrammatic representation of aswitchboard;

Fig. 7 is a diagrammatic sectional view of the :switchboard taken approximately along lines 7 7 of Fig. 6;

Fig. 8 is a 'diagram showing the basic selection scheme of the new system;

Fig. 9 illustrates an example of a line circuit;

Fig. 10 shows tens and units guard relaycircuits;

Fig. 1l illustrates a marker circuit which controls lselections in accordance with the numbers dial'led;

Fig. 12 represents an interrupter .circuit furnishing control and supervisory functions;

Fig. 13 illustrates an example of a loop dial trunk line;

Fig. 14 is a lockout relay circuit;

Fig. 15 `shows an example of a pay station circuit;

Figs. 16 and 17 taken together illustratea community automatic exchange or C. A. Xlink relay circuit 'associated with a finder and with a connector switch; and

Fig. 18 is a diagram showing the operation Aof counting relays included in the link relay circuit vshown -in Figs. 16-17.

The new system will now be discussed first in general 'terms referring to its component parts. These parts will then he described more in detail with reference to the above mentioned drawings, and the description of the component parts will be followed by explaining the operations incident to .establishing connections between calling and called lines. A description of the physical structureiof the apparatus which kis covered inthe previouslymentioned Patent No. 2,573,889 will for completeness and convenience 'be included in the following explanations to furnish a better basis for understanding the .new system features and lcircuit means.

The system and component parts in general It will be assumed that the system is provided to serve one hundred subscribers lines or, if desired, two hundred. 'it is understood, of course, that this is done for the purpose of giving an example and not to indicate any inherent limitations. The capacity of the system may be increased as desired, with no limitation as 'to the number 'of subscribers Ilines .to Vbe served.

A desired number of switches are arranged in pairs disposed side by side, one switch of each pair operating as a'nder'an'd the other as a connector. There may be as many pairs of such lnder-connector switches as required in any Vgiven circumstances. These pairs of switches 'form the switching mechanism of the system. Each (switch is structurally the same and its individual wiring is the same, whetherit is used as a nder or as a connector.

The switching mechanism, i. e.,'the plurality of pairs of finder-connector switches has a common line bank 'multiple comprising one hundred sets of removable conductor bars with three bars to each set, the three conductor bars in each set representing the line and test conductors, respectively, of a particular one of the one hundred subscribers lines. These conductor bars extend serially 'through the plurality'of pairs of finder-connector switches.

Each switch is provided with ten tens relays or magnets and with ten units relays or magnets. The operation of a tens magnet in conjunction with the operation of a units magnet determines the connection of three conductor bars which are individual to a subscibers line with three conductors of a switch bus which .is individual to the particular switch.

The conductors of the two switch buses of each pair of under-connectors switches terminate in a link circuit comprising a number of relays which exercise selection, control and supervisory functions. There is thus one such link circuit individual to each pair of finder-connector switches.

'The rplurality of pairs of `finder-connector switches forming the'switching mechanism of the system also have acomrnon allotterbank multiple comprising twenty removable conductor bars which extend serially through the switches just like the conductor bars of the line bank multiple. 'There are provided in each switch twenty contact ngers, one for making connection with each of `the allotter conductor bars. Ten of these contact fingers serve to connect with their associated alotter bars the ten tens magnets of the corresponding switch, and ten of the Acontact fngers serve in like manner to connect with their respective'alotter vbars the ten units magnets of the switch. The allotter lbars are connected with a common tens .and .units guard circui and also with a marker relay circuit whichis likewise common to all the finder-connectorswitches. An allotter magnet Yis provided in each switch for simultaneously actuating the twenty contact fingers kto extend the Aten tens andthe ten units magnets to ythe .tens and units guard circuits so as to determine fthe-association of the finder ofan idle finder-connector a `calling line, on incoming calls, and also to connect the ten tens and ten units magnets to the marker circuit in order to determine the selection of the called line by the connector under control of the marker circuit, on outgoing calls.

Each subscribers line has individual equipment in the exchange, referred to as the line circuit. Such line circuit, in accordance with the invention, comprises new circuit means for controlling the operation of the line and cutoff relays incident to the establishment of outgoing and incoming calls, respectively. The line and cutoi relays are provided with contacts which are serially related with corresponding contacts of line and cutot relays associated with other lines in a tens group of lines for the purpose of aiding the selection of a calling line by a finder in conjunction with the tens and units guard circuits. The guard circuits are common to the switching mechanism and determine which one of several idle links comprising a nder and a set of relays shall serve a call; that is, they determine the association of the line circuit of a calling line with an idle finder which in turn is associated with a set of link relays and a connector.

Also common to the switching mechanism, consisting of a plurality of pairs of nder-connector switches and an associated set of link relays is an interruptor circuit comprising a number of relays furnishing ringing codes, busy tone, overiiow busy tone, timing pulses for pay station tone, and alarm flashes for transmitting alarms over trunks. The invention also furnishes an example of a loop dial trunk circuit for handling trunk calls to a manual oiice.

These principal component parts and associated equipment will now be described with reference to the drawings.

The sit/itching mechanism The new switch and switching mechanism will be discussed first with reference to the diagram shown in Fig. 1.

'Ihe switch shown in Fig. 1 is one of several switches which form the mechanism. It comprises means for supporting ten rows of conductor bars disposed in parallel relation in one coordinate direction. As shown, these rows of conductor bars are disposed vertically. Each row has ten sets of bars with three bars in each set. These rows of bars form ten tens groups of conductors in the line bank multiple of the switch. Each bar extends serially through a number of switches disposed side by side in a direction extending perpendicular to the plane of the drawing. The bars are shown in the form of short, prominent lines in sets of three. Each set terminates in conductors which belong to the individual subscribers equipment in the exchange. There are thus ten tens groups of lines or bars, as indicated at the bottom of the diagram, from right to left, by prominent numerals 0010 20-30, etc. to 90. The first tens group contains conductors of lines 01-00. The second tens group contains conductors of lines 11-10, and so forth, and the tenth group contains the conductors of lines 91-90. The numbering scheme may be different from the one shown.

The ten tens sub-groups thus form in the other coordinate direction, horizontally as shown in the drawing, ten units groups of conductor bars, each units group comprising three rows of bars, ten in each row, as particularly indicated in connection with the top units row or group l and with the bottom units row or group 0. In the units group or row l there are the terminals of the lines 01-11-21-31, etc. to 91; in the units group 2 there are the terminals of the lines 02-92, and so forth; and in the units group 0 there are the terminals of the lines 00-90. These units groups 1 to 10 are marked by corresponding prominent numerals at the left of the diagram. Only the bars for the units groups 1, 2 and 0 have been shown throughout the bank multiple field of the diagram Fig. 1, while for the remaining units groups 3 to 9, the diagram indicates only the corresponding sets of bars in the two tens groups 00 and 90.

Each horizontally disposed individual row of conductor bars in each units group is provided with a bank spring having ten individual contact fingers, one for each conductor bar in the row, for making contact with such bar and thus connecting it with the bank spring. The bank spring associated with the topmost conductor bars in the units group 1" thus has individual contact fingers such as 25, one for each of the bars; the bank spring associated with the next lower row of bars in this units group has ten contact fingers such as 26, one for each bar in the row; and the bank spring associated with the bottom row of bars in this units group 1 is likewise provided with ten individual contact fingers such as 27, one for each bar in the row. The alternate contact iingers of each bank spring point in opposite directions. The bank springs may be of the type as disclosed in Patent No. 2,396,077.

Each and every units group is similarly equipped with three bank springs, one for each of its horizontally extending rows of conductor bars, and each bank spring has its ten individual contact iingers for connecting its associated bars with the corresponding bank spring. The diagram Fig. 1 shows the bank springs only in conjunction with the top and bottom units groups 1 and 0.

Associated with each tens group of lines or bars 00 to is a tens actuator comprising a member extending alongside its corresponding tens group having projections or extensions for actuating the individual contact fingers such as 25, 26, Z7 associated with each set of three conductor bars in the corresponding tens group. These ten tens actuators for the ten tens groups 00 to 90 are marked by numerals 30-39, inclusive. Each actuator is associated with a magnet, as indicated at 53-62. The magnets 53, 55, 57, 59 and 61 for the tens groups 00, 20, 40, 60 and 80, respectively, are adapted to actuate the actuator members 30, 32, 34, 36 and 3S, respectively, upwardly as shown in the drawing, so as to operate the individual contact fingers associated with the conductor bars in the respective tens groups to make contact with such bars. In similar manner the magnets 54, 56, 58, 60 and 62 are provided for operating the actuators 31, 33, 35, 37 and 39 associated with the tens groups 10, 30, 50, k70 and 90, respectively, downwardly as shown in the drawing, so as to operate the individual contact lingers in the respective tens group to make contact with their associated conductor bars.

Each bank spring is provided with an eleventh contact nger, as indicated at 96, 97, 98 in connection with the bank springs for the units group or row 1. A units actuator is provided which is associated with a magnet or relay 85, and when this units magnet operates, it displaces its units actuator 95 to move the eleventh contact fingers 96, 97, 98 into engagement with fixed contact members 99, 100, 101 which are connected to the conductors 102, 103, 104 of the switch bus. The operation of such a units magnet thus connects the three bank springs with the conductors of the switch bus. Each remaining units group 2 to 0 is provided with its own units actuator operating exactly like the units actuator 95 associated with the units group 1. The units actuator for the units group 0 is indicated by numeral 99 and its associated units magnet by numeral 91. Similar units actuators (not shown in Fig. 1) and associated units magnets are provided for each of the units groups 2 to 9. There are thus ten units actuators and associated magnets for the ten units groups 14 to 0. The xed contacts such as 99, 100, 101 of the various units groups are multipled to the switch bus conductors 102, 103, 104.

Any one of the one hundred sets of bars in the line bank multiple, each set having three contact bars representing, for example, a subscribers line, may be connected by the switch to the conductors of the switch bus. The switch bus in turn terminates vin 'the 'linder link. Assuming, for example, that line 01 is calling, the individual subscribers line circuit will be seized by an idle nder which may be the one shown in Fig.. l, the seizure being accomplished by the opera-tion of the tens actuator magnet 53 for the tens group G0L-'11 which operates the contact lingers 25, 26, 27 to engagethe three conductor bars of the calling line 01, thus extending these bars to the left, through the medium of the three bank springs, to the eleventh contact lingers 96, 97, d. Upon energization of the units magnet S5, the units actuator 95 is operated to cause the eleventh contact iingers 9.6, 97, 98 to make contact with the fixed terminals 9'9, 160, 101 of the switch bus. The line bars associated with the calling line "01 are now connected with the 'conductors 102, 103, 104 of the switch bus. Any one set of line bars associated with any one of the remaining subscribers" lines may be similarly connected with the conductors of the switch bus.

The finder, as noted before, is associated with a link relay circuit and the latter coacts with a connector which is structurally 'and functionally exactly like the linder. The called subscribers line is selected, in case of an outgoing call, in a similar manner as the calling line is seized by the nder incident to an incoming call. Assuming, for example, that line lll is calling line 90, the terminals of line 90 in the connector will be `extended to the eleventh contact lingers in the units group '"0, and units magnet 91 will then operate to actuate the units actuator 99 so as to connect the called line 90 with the terminals 102, 103, 104 of the switch bus, which lead to the associated relay circuit link.

As shown at the right of the diagram, Fig. l, there is also provided an allotter bank multiple comprising twenty individual conductor bars such as 112, 113,116, 117. Associated with each of these conductor bars is van individual contact linger. Thus, there is the contact linger 114 for Contact engagement with conductor bar 112, contact linger 115 for the conductor bar 113, contact linger 118 for conductor bar 116, and contact finger 119 for conductor bar 117. `An allotter actuator Ztl is provided which is structurally just like any of the tens actuators 30-39. The allotter actuator is `provided with lateral extensions or projections for simultaneously operating the contact lingers such as 114, 115, 118, 119, etc., into engagement with their associated allotter bars such as 112, 113, 116, 117. The allotter magnet is indicated at 127.

The ten allotter bars l to are the units allotter bars and the ten allotter bars to 0l) are the tens allotter bars. All these bars are connected with the tens and units guard circuits to aid inthe selection of calling lines, that is, to aid in the operation of an idle linder, to connect with a calling line, and are also connected with the marker circuit to aid in the selection of a called line by the connector associated with the finder, the marker circuit interpreting the dial impulses delivered to the link circuit which is individual to the particular pair of linderconnector switches.

As will be presently shown, each of the tens magnets 53-62 and each of the units magnets 85-91 is provided with contact springs which are actuated upon operation of the respective tens and units magnets to furnish a holding circuit therefor.

The actual switch structure shown in Figs. 2-5 will be easily understood, bearing in mind the explanations given with reference to the diagram shown in Fig. l.

As shown in Figs. 2 5, the switch comprises a generally rectangular frame formed by a pair of rail-like members 11-12 which are joined on top by an angular plate 13 forming a ledge 14 and at the bottom by an angular plate 15 forming the ledge 16. Secured to the rail members 11-12, as shown particularly in Figs. 3 and `5, are live plates of insulating material, for example, Bakelite.` Only two of these plates are shown in full, marked 17 and 20, and two plates 18 and 19 are show-n in fraction. YEach plate is provided with eighty-eight holes disposed `in eleven vertically extending parallelzrows, eight holesin a row. When mounted on the rail members 1.1-1.2, as shown, these plates thus form eleven vertically extending parallel rows of holes with forty holes in each row7 or a total of 440 holes. Supported in these holes are the conductors of the line bank multiple and, inasmuch as it is assumed that the subscribers line circuits have three conductors, namely, two line and one. test conductor, only three hundred holes would be required for theline bank multiple. The additional ten holes in each of ten vertical rows of the structure are provided in accordance with one object of the invention so as to adapt the switch for accommodating three hundred line multiple bars forming the terminals of one hundred lines each having three conductors, or, alternatively, four hundred line multiple bars forming the terminals ol'` one hundred lines each having four conductors. The eleventh vertical row of holes accommodates the conductor bars for the allotter bank multiple, which is one of the new features of the invention.

The switch structure Will be described later on in connection with a system in which the subscribers line equipment provides for 'three conductors. Accordingly, only thirty holes in each of ten vertically extending rows of holes are actually used for receiving the metallic conductor bars forming the line bank multiple. These bars are inserted through the corresponding holes in the insulating plates of a number of switches disposed side by side, the bars extending serially through all such switches. There are thus again in the line bank multiple ten vertically disposed parallel rows of thirty bars to each row, each row containing the terminals of ten lines each having three conductors. These are the tens sub-groups of lines numbered 00-90 in Fig. l.

The numbering scheme may be that already discussed in connection with Fig. l, identical numerals in Figs. Z-S referring to identical parts. l

The bank springs associated with each horizontal row of line and test bars in each units group or level ofthe switch is a phosphor bronze spring having ten individual contact fingers, one for making contact with each of the bars in the corresponding row. these bank springs with their contact lingers is similar to the one described in previously mentioned Patent 2,396,077. ln the present case, however, the free ends of the contact lingers are formed to point in alternately different directions. linger 25 for making contact with the topmos't Vbar of line 01 points upwardly, as also shown in Fig. l, in the direction `of the topmost bar (il, and all vertically downwardly successive similar contact lingers also point upwardly in the direction of their associated contact bars. The Contact lingers in the next tens .group point downwardly, and the same scheme is repeated from tens group to tens group, the contact lingers of the bank springs, pointingalternately upwardly and downwardly in the direction of their associated contact bars. The contact lingers associated with the line and test bars of 'the ten verticaly extending tens groups have been Vomitted in Fig. 5 in order to avoid confusing the drawing. In AFigs. 2 and 3, the line and test bars have been shown within the top portion of the multiple bank. v

Each tens actuator Sli-'59 provided for vthe respective tens groups and also the allotter actuator is "an angularly shaped member made of a .suitable insulating inaterial `having one edge serrated to form the lateral extensions or projections for operating the various contact lingers of the bank springs, the other edge extending rearwardly as shown in connection with the allotter Valttuator 1720 at 13h in Fig. 5, thus providing a structure which resists warping. A guide 131 (Fig. 5 is provided which is a striplike member Aextending transversely The structure of v Thus, the free end of the contact through the structure in back of the ten tens actuators and the allotter actuator, respectively. This guide has a serrated edge providing notches, one for each of the rearwardly directed edges such as 130 of each actuator to guide and support such actuator. A cross-sectionally U-shaped metallic member may be used for each tens actuator and for the allotter actuator, respectively, in place of the angular member, with holes in its base for the various contact fingers to be operated thereby and carrying a similarly apertured insert of insulating material.

Each tens `actuator Sti-39 is mounted at one end in engagement with a spring member forming a snubber and an end guide therefor, as indicated in Fig. 2 at 40 and 41, being the snubber and end guide members for the tens actuators 30 and 31, respectively. The allotter bar 120 is at its upper free end likewise associated with such a spring and snubber guide member, as indicated in Figs. 2 and 5. The spring snubber and end guide member for the tens actuator 39 is indicated in Fig. 2 at 50. The snubber and end guide member for the remaining tens actuators and for the allotter actuator are shown in Fig. 2 but are not marked by reference numerals. The opposite end of each tens actuator and also of the allotter actuator is pivotally associated, by means of a cliplike member such as indicated in Figs. 2 and 5 at 51 for the tens actuator 39 and at 125 for the allotter actuator 120, with the armature of its corresponding tens magnet 53-62 and of the allotter magnet 127, respectively. Thus the tens actuator 30 is provided with the cliplike member 51 which associates the actuator with the armature 52 of the tens magnet 53, being the operating magnet for the tens group 90 which contains the line and test bars belonging to lines 01 to 00. The tens actuator 31 is similarly associated with the tens magnet 54 serving the conductor bars of the tens group of lines containing the numbers 11 to 10. The remaining tens actuators 32-39 are in a similar manner associated with their corresponding tens magnets 54-62, respectively. T he allotter actuator 120 is in like manner associated with the armature 126 of the alotter magnet 12.7.

It will be clear from the foregoing description that the tens actuators are disposed for operation in alternately different directions, as already described in connection with Fig. 1. The tens actuators for the tens subgroup 00, 20, 40, 60 and 80 are operatively displaced upwarly responsive to the actuation of the associated tens magnet 53, 55, 57, 59 and 61, While the tens actuators for the tens sub-groups 1G, 30, 50, 7i) and 90 are operatively displaced downwardly responsive to actuation of the associated tens magnet 54, 56, 58, 60 and 62. The allotter actuator 120 is displaced downwardly by the actuation of the associated allotter magnet 127.

The tens magnets 54, 56, 58, dit and 62 and the allotter magnet 127 are mounted on the ledge 16 of the angular bottom plate 15, of the switch while the tens magnets 53, 55, 57, 59 `and 61 are mounted lon the ledge 14 of the angular top plate 13. Numeral 53a indicates the core of the tens magnet 53 coacting with the armature 52, and numeral 62a indicates the core of the tens magnet 62 which coacts with the corresponding armature associated with the tens actuator 39. Reference numerals for the cores of the remaining tens magnets have been omitted.

As previously stated in connection with the description of Fig. 1, each of the tens actuator magnets is provided with a contact which is closed by its associated armature upon energization thereof and consequently upon actuation of the associated tens actuator. Thus, as is particularly apparent from Figs. 2 and 5, the tens magnet 53 for the tens actuator 30 is provided with the contact 70 which is actuated by an insulating nipple 71 carried by the armature 52, and when the tens magnet 53 energizes it attracts its armature 52, displacing the tens actuator 30 and also closingthe contact 70, which is done 10 for the purpose of providing a holding circuit for the magnet 53. Each of the remaining tens magnets 54--62 is provided with a similar holding contact.

At the front of the switch is provided a cross-sectionally U-shaped channel member having the base and the side walls 76-77, as particularly shown in Figs. 2 and 4. This member is suitably secured to the switch frame member 11. Within this channel member are mounted the ten units magnets, seven of which are indicated in Fig. 4 at 78-84. Each units magnet has an armature, as indicated 'at 85, S6, 87, 8S, 89, 90, 91, being the armatures of the magnets 78-84, respectively. Each armature has an arm such as 92, 93, 94, 95 which projects angularly rearwardly, as indicated in Fig. 2 in connection with armatures S5, 86, and 91, respectively. Each arm carries at its free end an insulating member or units actuator as indicated in Fig. 2 at 95, 97, 98 `and 99, respectively, each insulating member having a number of projections for actuating the associated eleventh contact ngers of the corresponding bank springs in the respective units groups. Thus the projections extending from the insulating member carried by the arm 92 of the armature 85 are adapted to actuate the three eleventh contact tingers 96, 97, 98 to make contact with the three stationary contact members 99, 100, 101 which in turn are connected with the multiple conductors 102, 103, 104 of the switch bus. Each set of eleventh contact fingers in each units group comprising three flngers is similarly operated into engagement with the associated stationary contacts which are multiplied to the conductors of the switch bus, as already explained in connection with Fig. l.

It will be observed that each of the units actuators such as shown in Fig. 2 at 95, 97, 98, 99, has four projections, while only three are utilized for actuating the three Aassociated eleventh contact fingers of the corresponding bank springs. The fourth projection, which is not used in the present case, may be employed in structures serving subscribers lines having four lines and test conductors instead of three, as has been assumed in the present case.

Each of the units magnets is also provided with an individual contact which is operable by its armature upon attraction thereof. As shown in Figs. 2 and 4, the individual contacts thus associated with the units magnets 78-84 are indicated at 105, 106, 197, 108, 109, 11i) and 111. As in the case of the corresponding individual holding contacts of the tens magnets, these contacts are provided for the purpose of furnishing holding circuits for the corresponding units magnets.

The conductors for the `allotter bank multiple are accommodated in the eleventh vertical row of holes at the right end of the switch, as shown in Fig. 2, and at the left, as shown in Fig. 3. The insulating plates supporting the line bank multiple bars 'and the allotter bank bars are uniformly made, land there are thus in the eleventh vertical row forty holes, with only twenty utilized for accommodating the twenty allotter bars required in accordance with the explanations furnished in discussing Fig. l. Each allotter bar is again a'stainless steel bar just like the conductor bars for the line blank multiple, and each bar extends serially through a group of switches. The explanations given in discussing the diagram, Fig. 1, are believed to be suficient for an understanding of the structure of the allotter bank multiple and its associated allotter actuator operable by the allotter magnet 127, as shown in Figs. 2-5. The correspending parts are marked in these gures in accordance with the marking in Fig. 1.

The new switch structure differs in several respects from prior structures. The arrangement of some of the tens actuator magnets at lone end of the switch and other at the other end is a space-saving device which permits use of more powerful magnets, one individually for each actuator, also contributing to circuit simplification. The

provision of the allotter bank multiple with its allotter springs and magnet contributes to structural simplification as compared with prior structures. The provision of individual holding contacts, one for each tens and units magnet, contributes toward circuit simplification and reliability of operation. Only one switch structure need be provided to serve as a finder or as a connector, as may be required. The switch structure is standardized and, as has been said before, can accommodate a line bank multiple having sets of conductor bars, each set with three or four bars for use, respectively, with lines having three or four conductors.

The arrangement of a plurality of pairs of finder-connector switches and associated relay and other equipment on a board is diagrammatically indicated in Figs. 6 and 7. The board is a suitable frame and sheet material structure having two walls diagrammatically indicated at 15@ and 151, the bottom 152 and the top 153. Within the board may be provided suitable cross and mounting menibers 154, 155, 156 which define the shelves or spaces for the various groups of apparatus.

The sets of link circuits, one for each pair of finderconnector switches, as well as the set of relays forming the common marker circuit and common interrupter circuit may be suitably disposed within the spaces defined by the rectangule 157. The sets of relays forming the common tens and units guard circuits, as well as the individual line equipment, may be disposed in the spaces defined by the rectangles 158. Each set of equipment is provided with jack contacts and is jacked into corresponding jack terminals provided in the board.

The switches, each of which is provided with jack contacts as shown in Fig. 2 at 135, are removably arranged on a shelf side by side, each being jacked into corresponding jack terminals associated with the shelf. A group of the switches is disposed in the shelf on either side of the bank jack 140 which has been described in the U. S. Patent No. 2,485,986 and need not be further referred to `at this place, except to state that it is a structure carrying an insulating plate provided on either side with jack terminals for receiving from each side the conductor bars forming the line bank multiple and the allotter multiple, respectively. At each end of the shelf is an end guide, as indicated at 141142, which comprises an insulating plate having holes corresponding to the holes in the insulating plates in each switch for starting the insertion of the conductor bars through the group of switches until the free end of each bar engages its jack terminal in the bank jack 140. A group of three bars 143 is shown inserted through the end guide 1141. The bars extend through all the switches at the left of the bank jack 140, the inner ends thereof terminating in the jack terminals therein. Three similar bars 143 are shown which are inserted from the right of the mechanism through the end guide 142 and are threaded through the holes in the insulating plates of the successive switches until their inner ends are in engagement with corresponding jack terminals in the bank jack 149. There are three hundred line 'and test bars and twenty allotter bars extending into the switch structure from the left through the end guide 141 and three hundred twenty similar bars extending into the switch structure through the end guide 142. These bars being joined at the bank jack 14@ thus divide the structure into two distinct groups each of which can be manipulated individually and both of which form the switching mechanism. in other words, the conductor bars of the line bank multiple and of the allotter lbank multiple at the left of the bank jack 140 are conduetively joined with corresponding conductor bar-s ere tending through the switches at the right of the bank jack 140. The arrangement simplifies addition and removal of switches for repair and other purposes, as pointed out in previously mentioned Patent No. 2,485,986.

There are in the switch shelf, as shown in 1Eig. 6, fourteen pairs of switches, each pair comprising a finder The switch shelf is pivotally mounted at -146. ltl

is thus possible to rotate the entire switching mechanism, with all its fourteen pairs of finder-connector switches, from the full-line position shown in Fig. 7 to the dottedline position, and in this position the line bank multiple bars as well as the allotter bars can be withdrawn from either end of the structure, as indicated in connection with the bar 143. If it is necessary, for example, to replace or repair a switch or to add switches to the mechanism, all of the bars forming the line bank multiple and the allotter bank multiple are withdrawn, whereupon any one of the switches in the corresponding group can be removed by pulling it out forwardly from engagement with the associated jack. The mechanism is not put out of operation, as calls may be handled over the switches of the group at the other side of the bank jack 140. The pivot points 145-146 are rearwardly offset from the center line to avoid strain on the cable extending from the contacts of the bank jack.

The selection scheme has been briefly explained iu connection with the description of Fig. l. It will aid in understanding the invention to discuss the selection scheme a little more in detail with reference to Fig, 8.

The figure illustrates in a schematic manner two finders and two connectors of a l00-line system. For the sake of clarity, only nine of the one hundred lines are shown, and each is represented by a single conductor, although actually three or more conductors are of course provided in the switchboard for each line. So far as the functions of the finders and connectors are concerned, it will be sufficient to say at this place that a connection is completed in the following steps: (1) a calling line automatically engages an idle finder and connector for the duration of the connection; (2) the finder controlled by the line relay of the calling line connects such line to the connector by way of the associated link relay circuit; (3) the calling party then dials the desired number which is received by the connector relays; and (4) the connector relays cause the connector to make connection to the calledV line, if idle.

Assuming that line 31 is calling and that finder 1 is seized for the call, the tens actuator 3i) in this finder is operated to connect lines 30-39 to the bank springs of the switch, and units actuator 1 is operated to connect its bank springv fingers to the switch bus conductors. The other nine bank spring sets remain open at their unoperated units actuator contacts. Line 31 is now connected to the associated link relay circuit provided for the pair of switches, namely, the finder 1 and connector 1.

When the desired number is dialled, the connector relays in the link circuit function to cause operation of a tens actuator and of a units actuator in the connector. Assuming that No. 23 is dialled, the tens actuator 20 of the connector 1 functions to connect lines 2li-29 to the connector bank springs, and units actuator 3 connects its eleventh bank spring fingers to the terminals of the connector bus conductors, thus completing the connection from the finder 1 through the connector 1 and its relays to line 23. The other nine lines of the group Ztl-29 are kept open at the other units actuator contacts.

The complete connection may be traced from line 31 in the upper left hand corner of the diagram Fig. 8, following the horizontal multiple bar of this line to tens actuator 30 of finder 1, then through the contacts closed by tens actuator 30 and the bank spring fingers actuated by units actuator 1 to the finder bus conductor through the link relay circuit and the connector bus conductor, to the bank spring finger actuated by units actuator 3, and through the bank spring to its contacts closed by 13 tens actuator 20 and from there through the line bank multiple to line 23.

Another call may be set rn over the pair of switches forming the finder 2 and the connector 2 while the rst call is in progress, without in any way affecting the iirst call. Fig. 8 illustrates only two finders and two connectors, the additional finders and connectors being in every respect the same as those shown. For clearness, all tens actuators in Fig. 8 are shown as operating upward; in the actual switch, as explained before, the tens actuators lll, 30, 5t), 70 and 9G operate downward.

The explanations so far deal with a 1GO-line system, but the same selection scheme is applied to systems of any size. The lGOdine group may be enlarged to two hundred lines by using two lOO-line switches for each nder and connector. For still larger systems, one or more stages of switches, wired as selectors, may be interposed in well known manner between the finder and connector groups. Thus automatic telephone systems of any desired size may be built up.

The line circuit A line circuit such as shown in Fig. 9 may be provided for each subscribers line. It represents the subscribers individual line equipment at the exchange. The two line conductors shown in prominent lines at the top of the figure extend to the left where they connect with the subscribers telephone set. At the right these two conductors and a test conductor T extend to the corresponding line and test conductor bars provided for the particular subscriber in the line bank multiple of the switching mechanism which comprises the pairs of finder-connector switches. The line is thus accessible to any one pair of finder-connector switches.

The line circuit coacts with the tens and units guard relays shown in Fig. l and may be conveniently considered in groups of ten, serving ten lines with the same tens digit in their line numbers. The drawing shows the line circuit for line No. l in any tens group, for example, line 0l in the tens group, comprising lines 0l to 00, as shown in Fig. l. Of the remaining line circuits 2 to 0 in this group, Fig. 9 shows only serially related contacts controlled by the corresponding line relays LR and the cutoff relays CO of the group. Conductor TN terminates in the tens guard relay T1 (Fig. l0) provided for the particular tens group, and conductors U1, U2, etc. to Uil terminate each in units guard relays U1, U2, etc. to Uil, as shown in Fig. 10.

The contacts operated by the line and cutoff relays LR and CO are indicated along the axis of the respective relays and are marked by low numerals to avoid undue complications in the description as well as in the drawings. In order to avoid confusion, it is necessary to keep in mind the scheme that has been adapted for designating the various parts. The line relay LR, for example, has three transfer contacts designated by numerals 12, 2 and 5, respectively. The cutoff relay CO has three transfer contacts designated l5, l2 and 2, respectively, and in addition thereto a break contact S. Each contact will be referred to in terms of function and association with its respective relay. Thus, the circuit which results on incoming calls, that is, initially when the subscriber lifts the receiver to make a call, will be described as extending from battery on conductor LR-BAT, through the upper winding of LR, COblS (which is the break contact l5 of the CO relay) over the line to COb12 (which is the break Contact 12 of the CO relay), to ground, causing energization of the line relay LR. The two contacts 15 and 12 of the cutoff relay CO are thus plainly identified, the letter b in the designations CObllS and COb12 referring to the break side of each contact, that is, to the normal position in which the contacts are shown in the drawing. Similarly, designations such as LRml2 or COml2 mean the make contacts 12 of the re- 14 spective relays, that is, the operated position of the two contacts.

Contacts marked by a numeral and an `asterisk indicate that the corresponding contact is adjusted for makebefore-break operation.

This general scheme of identifying contacts will be adhered to throughout the description of the various circuits.

Referring now to the line circuit shown in Fig. 9: The lifting of the hand set at a subscribers station closes a D. C. bridge across the line operating LR from battery on LR-BAT through the upper winding of LR, COblS over the line to COb12 to ground. LR closes a circuit from tens guard conductor TN over LRmS, CObZ, to one of the units conductors Ult-U0, depending on the corresponding tens and units digits of the calling line. This operates the tens guar-d relay and the units guard relay (Fig. l0) corresponding to the tens and units digits of the calling line. These relays cause the finder switch of an idle link (Figs. l6-17) to select the calling line.

The line relay LR also opens the series circuit to the contact LRbS of the next line (line 2) to prevent double selections, if two or more lines should happen to be callat the same instant, as will be explained in connection with the description of the tens and units guards shown in Fig. 10.

The terminal TNO (bottom of Fig. 9) is provided for testing the series circuit from the conductor TN through all ten lines.

The finder (Fig. 16) selecting the calling line connects ground to the test wire T, holding the line relay LR and operating the cutoff relay CO from ground on test wire T over the lower winding of LR, LRmlZ, upper winding of CO to battery on CO-BAT. The cutoff relay CO opens the circuit from tens guard conductor TN to the associated units guard lead such as U1 at CObZ, releasing the tens and units guard relays and reestablishing the circuit from conductor TN to contact LRmS over COmZ so that other lines in the lO-liue group can make calls. For example, if line 2 in the same tens group should now make a call, thetens guard relay T1 and the units guard relay U2 (Fig. l0) will be operated in a circuit extending over conductor TN, LRmS, COmZ (line and cutoff relays of line 1 being energized), LRmS of line 2 (which initiates a call), COb2 (of line 2), conductor U2 to the units guard (Fig. 10) and winding of units guard relay U2.

With the line relay LR and the cutoff relay CO operated, the windings of both relays are disconnected from the plus and minus conductors of the line at COblS, LRblZ, COblZ and LRb2, clearing the line for dialling and talking.

An auxiliary circuit is closed at this instant for the cutoff relay CO from ground through COmlZ, lower winding of the cutoff relay CO, LRmZ, resistor r, to battery on CO-BAT for purposes which will be explained later on.

On outgoing calls, that is, when the line is called, the connector switch (Fig. 17) selecting the line connects ground to its test wire T, operating the line and cutoff relays LR and CO in series over the lower winding of LR, CObS, upper winding of CO, to battery on C10-BAT. Due to a much larger number of turns in .its winding, the line relay LR operates before the cutoif relay CO, maintaining the circuit over LRmlZ before the cutoff relay CO can break it at CObS. The subsequent functions of the circuit are the same as for incoming calls.

When the connection is released, either on an incoming call or on an outgoing call, ground is removed from the test Wire T, opening the circuit of the line relay LR, While the cutoff relay CO is still being held over COmlZ, lower winding of CO, LRmZ, resistor r, to battery on CO-BAT. The release of LR before breaking this circuit for CO connects the cuto relay CO momentarily to the line loop from battery on CO-BAT through the upper winding of CO, LRblZ, COmlS, over the line to LRb2, lower winding of CO, and COm12 to ground. If the hand set. 

